I don't think Hannity has any advance knowledge of what (if anything) Assange is planning to release. Lately Assange has been focused on the Catalan independence movement, so if he does have something big to come out it may be related to that.
As far as the Russia-Clinton pay-to-play stuff... this is already pretty well documented and widely known... has been for quite some time. No one in government (or the MSM) cared about it when it came out, and now its just old news.
Too many in the swamp are up to their eyeballs in corruption. Taking on the Clintons means they go down too... its sort of a MAD (mutually assured destruction) sort of arrangement that's been developed between the Clintons and the swamp over decades.
Hannity & Assange communicate more often than you apparently realize. Pay for play would not be the topic. Russian collusion with Obama & Hillary or involvement in Seth Rich’s murder, or even both, are my guesses.